/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
package org.apache.iotdb.tsfile.read.query.timegenerator;

import org.apache.iotdb.tsfile.exception.write.UnSupportedDataTypeException;
import org.apache.iotdb.tsfile.read.common.Path;
import org.apache.iotdb.tsfile.read.expression.ExpressionType;
import org.apache.iotdb.tsfile.read.expression.IBinaryExpression;
import org.apache.iotdb.tsfile.read.expression.IExpression;
import org.apache.iotdb.tsfile.read.expression.impl.SingleSeriesExpression;
import org.apache.iotdb.tsfile.read.filter.basic.Filter;
import org.apache.iotdb.tsfile.read.query.timegenerator.node.AndNode;
import org.apache.iotdb.tsfile.read.query.timegenerator.node.LeafNode;
import org.apache.iotdb.tsfile.read.query.timegenerator.node.Node;
import org.apache.iotdb.tsfile.read.query.timegenerator.node.OrNode;
import org.apache.iotdb.tsfile.read.reader.IBatchReader;

import java.io.IOException;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;

/**
 * All SingleSeriesExpression involved in a IExpression will be transferred to a TimeGenerator tree
 * whose leaf nodes are all SeriesReaders, The TimeGenerator tree can generate the next timestamp
 * that satisfies the filter condition. Then we use this timestamp to get values in other series
 * that are not included in IExpression
 */
public abstract class TimeGenerator {

    private HashMap<Path, List<LeafNode>> leafNodeCache = new HashMap<>();
    private HashMap<Path, List<Object>> leafValuesCache;
    protected Node operatorNode;
    private boolean hasOrNode;

    public boolean hasNext() throws IOException {
        return operatorNode.hasNext();
    }

    public long next() throws IOException {
        if (!hasOrNode) {
            if (leafValuesCache == null) {
                leafValuesCache = new HashMap<>();
            }
            leafNodeCache.forEach(
                    (path, nodes) ->
                            leafValuesCache
                                    .computeIfAbsent(path, k -> new ArrayList<>())
                                    .add(nodes.get(0).currentValue()));
        }
        return operatorNode.next();
    }

    /**
     * ATTENTION: this method should only be used when there is no `OR` node
     */
    public Object[] getValues(Path path) throws IOException {
        if (hasOrNode) {
            throw new IOException(
                    "getValues() method should not be invoked when there is OR operator in where clause");
        }
        if (leafValuesCache.get(path) == null) {
            throw new IOException(
                    "getValues() method should not be invoked by non-existent path in where clause");
        }
        return leafValuesCache.remove(path).toArray();
    }

    /**
     * ATTENTION: this method should only be used when there is no `OR` node
     */
    public Object getValue(Path path) throws IOException {
        if (hasOrNode) {
            throw new IOException(
                    "getValue() method should not be invoked when there is OR operator in where clause");
        }
        if (leafValuesCache.get(path) == null) {
            throw new IOException(
                    "getValue() method should not be invoked by non-existent path in where clause");
        }
        return leafValuesCache.get(path).remove(0);
    }

    public void constructNode(IExpression expression) throws IOException {
        operatorNode = construct(expression);
    }

    /**
     * construct the tree that generate timestamp.
     */
    protected Node construct(IExpression expression) throws IOException {

        if (expression.getType() == ExpressionType.SERIES) {
            SingleSeriesExpression singleSeriesExp = (SingleSeriesExpression) expression;
            IBatchReader seriesReader = generateNewBatchReader(singleSeriesExp);
            Path path = singleSeriesExp.getSeriesPath();

            // put the current reader to valueCache
            LeafNode leafNode = new LeafNode(seriesReader);
            leafNodeCache.computeIfAbsent(path, p -> new ArrayList<>()).add(leafNode);

            return leafNode;
        } else {
            Node leftChild = construct(((IBinaryExpression) expression).getLeft());
            Node rightChild = construct(((IBinaryExpression) expression).getRight());

            if (expression.getType() == ExpressionType.OR) {
                hasOrNode = true;
                return new OrNode(leftChild, rightChild, isAscending());
            } else if (expression.getType() == ExpressionType.AND) {
                return new AndNode(leftChild, rightChild, isAscending());
            }
            throw new UnSupportedDataTypeException(
                    "Unsupported ExpressionType when construct OperatorNode: " + expression.getType());
        }
    }

    protected abstract IBatchReader generateNewBatchReader(SingleSeriesExpression expression)
            throws IOException;

    public boolean hasOrNode() {
        return hasOrNode;
    }

    protected abstract boolean isAscending();

    public abstract Filter getTimeFilter();
}
